Of the deer I've personally seen shot or shot with the 30-30 myself,They seem to drop quicker using 125 gr(sierra flatnose hollow point),or 150 grof slightly softer construction. The ol 30-30 don't have thespeed of faster rounds so it seems to me that bullet expansion is a bit more critical than with a bullet traveling at 2800-3100 fps. it don't have the sheer horsepower of faster rounds.With a well placed shot and easily expanding bullets-it'll ALWAYS be plenty for deer. I just can't agree with using the heavier 170 gr bullet in it as it don't expand as easy as the lighter bullets. The marlin I've had since the 70s LOVESthe sierra 125 gr hps and does a great job of putting them down within it's limits. It STILL wears the same old steel tube (bombproof) weaver w/duplex and "microtrac" K2.5.